An experimental framework to assess biomolecular condensates in bacteria

Area of Science:

• Cell Biology
• Biophysics
• Microbiology

Background:

• High-resolution imaging of biomolecular condensates in living cells is crucial for linking in vitro and in vivo observations.
• Studying these condensates in bacteria is challenging due to inherent resolution limitations.

Purpose of the Study:

• To present an experimental framework for probing biomolecular condensate formation, reversibility, and dynamics in Escherichia coli.
• To determine the fundamental nature of biomolecular condensates within bacterial cells.

Main Methods:

• Development of an experimental framework to observe condensate-forming proteins in live bacterial cells.
• Analysis of condensate formation thresholds, reversibility under environmental shifts (temperature, concentration), and internal dynamics.
• Utilizing IbpA as a potential reporter to distinguish bacterial condensates from insoluble protein aggregates in vivo.

Main Results:

• Biomolecular condensates in bacteria form above a critical concentration threshold and retain a soluble fraction.
• Condensates demonstrate reversibility, dissolving upon changes in temperature and concentration.
• Observed dynamics indicate internal rearrangement and exchange between condensed and soluble protein fractions; IbpA shows distinct colocalization patterns.

Conclusions:

• The developed framework enables rigorous, accessible, and generalizable sub-micron scale investigation of bacterial biomolecular condensates.
• The findings provide insights into the behavior and properties of protein condensates in bacteria.
• IbpA shows promise as a tool for differentiating bacterial condensates from aggregates in vivo.